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Proceedings Paper

New UV optic for submicron laser processing with a frequency quadrupled Nd:YAG laser
Author(s): Peter B. Heekenjann; Holger Schmidt
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Paper Abstract

A new UV-optic with an integrated autofocus sensor has been developed for submicron laser processing. In general, a distinction can be made between reflective and refractive objectives. Both have different advantages and disadvantages and, therefore, must be adapted to the application. For refractive objectives designed for UV-purposes, only a limited number of materials are available. With a small spectral bandwidth, such as that for some laser sources, an all quartz lens can be used. The frequency quadrupled Nd:YAG laser already has in its basic set-up a spectral bandwidth of less than 100 GHz. In the seeded mode, only one longitudinal mode will be excited. In order to achieve focus diameters below 0.5 micrometers , at least an N.A. of 0.65 is necessary. Such an objective has been designed and built at the Laser Zentrum Hannover (LZH). For this objective, automatic focussing aids are necessary. They have to ensure that the focal plane is within the depth-of-focus (DOF), which is below +/- 0.4 micrometers for the designed objective. Currently, all available sensors in this area show major drawbacks concerning the desired flexibility in being used for different laser processes. Therefore, a sensor, based on the autofocus principle, has been modified and built at the LZH. The results have proven that the resolution and the mean deviation are within the desired range (DOF).

Paper Details

Date Published: 4 November 1994
PDF: 10 pages
Proc. SPIE 2246, Laser Materials Processing and Machining, (4 November 1994); doi: 10.1117/12.193107
Show Author Affiliations
Peter B. Heekenjann, Laser Zentrum Hannover eV (Germany)
Holger Schmidt, Laser Zentrum Hannover eV (Germany)

Published in SPIE Proceedings Vol. 2246:
Laser Materials Processing and Machining
Rolf-Juergen Ahlers; Peter Hoffmann; Hermann Lindl; Ruediger Rothe, Editor(s)

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